Bush assembly

ABSTRACT

A bush assembly comprising a component having a bore, a bush fitted in the bore and having a flange that extends radially outwardly over a surface of the component surrounding the bore, and a seal assembly for sealing the interface between the flange and the surface of the component, wherein the seal assembly includes a seal member and a layer of sealant between the seal member and the interface between the flange and the surface of the component. Also a method for sealing a bush, a kit of parts for forming a bush assembly, and a clamping tool for forming a bush assembly.

FIELD OF THE INVENTION

The invention relates to a bush assembly; to a kit of parts for forminga bush assembly; to a method for sealing a bush; and to a clamping toolfor forming a bush assembly.

BACKGROUND OF THE INVENTION

A bush may be fitted in a bore in a component to provide an innersurface within the bore. The inner surface may, for example, provide abearing surface for receiving a rod or shaft which passes through orinto the component. The bush may have a flange which locates the bushwithin the bore and covers the interface between the bush and the boresurface.

Over time, the performance of the bush may be reduced, for example dueto degradation of the bush and/or the bore surface. Degradation of theinterface between the bush and the bore may occur due to contamination,for example by water, oil, dirt or debris, resulting in surfacecorrosion of the bush and/or bore. The flange may act to reducecontamination of the interface between the bush and the bore, and alayer of sealant may be applied over the bush flange and the surface ofthe component to seal the bush. However, contamination/corrosion of thebush may still occur, particularly if the layer of sealant becomesdamaged or degraded, for example due to mechanical wear, corrosion orage hardening.

In some cases, it may become necessary to replace the bush, or tore-bore the component and fit a new bush having a larger outsidediameter to fit the new bore, or even to replace the component entirelyif extensive corrosion has occurred. The problem of contamination ofbushes may present a particular problem for large bush assemblies, inwhich the parts may be difficult and expensive to maintain, monitor andreplace. If the component is an aircraft component, for example a mainlanding gear component, these maintenance tasks may require the aircraftto be removed from service while the maintenance tasks are carried out.Replacing a main landing gear component due to a degraded bush assemblymay be time consuming, expensive and wasteful of materials.

SUMMARY OF THE INVENTION

The invention relates to a seal for sealing a bush assembly. The sealincludes a seal member which sits over a flange of the bush which isfitted in a bore of a component and a material for sealing between theseal member and the flange/component.

A first aspect of the invention provides a bush assembly comprising acomponent having a bore, a bush fitted in the bore and having a flangethat extends radially outwardly over a surface of the componentsurrounding the bore, and a seal assembly for sealing the interfacebetween the flange and the surface of the component, wherein the sealassembly includes a seal member and a layer of sealant between the sealmember and the interface between the flange and the surface of thecomponent.

A second aspect of the invention provides a kit of parts for forming abush assembly, the kit of parts comprising a bush for fitting in a borein a component, a seal member and a sealant material; wherein the bushhas a flange that is adapted to extend radially outwardly over a surfaceof the component surrounding the bore when the bush is fitted in thebore; and wherein the sealant material is for providing a layer ofsealant between the seal member and an interface between the flange andthe surface of the component such that the layer of sealant and the sealmember form a seal assembly for sealing the interface between the flangeand the surface of the component.

A third aspect of the invention provides a method for sealing a bush,the method comprising the steps of: providing a component having a borewith a bush fitted in the bore, the bush having a flange that extendsradially outwardly over a surface of the component surrounding the bore;arranging a seal member with respect to the bush; and introducing asealant material so as to provide a layer of the sealant materialbetween the seal member and an interface between the flange and thesurface of the component to form a seal assembly for sealing theinterface between the flange and the surface of the component.

A fourth aspect of the invention provides a clamping tool for applying aclamping force for sealing a bush installed in a bore in a component,the tool comprising a first part, a second part and a clampingmechanism; wherein the first part comprises a recess which is adapted toengage a seal; the second part is adapted to engage a surface of thecomponent which opposes and faces away from a surface of the componenton which the seal is provided; the clamping mechanism is operable tomove the first part relative to the second part, thereby applying aclamping force to the seal; and wherein the clamping tool includescentring means for centring the clamping tool relative to the bush.

The seal assembly may be adapted to substantially prevent the ingress ofcontaminants into the interface between the flange and the surface ofthe component, for example to prevent the ingress of water or oil ordirt or debris. The seal assembly may, therefore, reduce or eliminatethe ingress of water and/or any other contaminants into the interfacebetween the bush and the surface of the bore.

By reducing or preventing the ingress of contaminants between the bushand the component, the seal assembly may reduce the rate of degradationof the bush and/or the component, thereby reducing the need formaintenance activities, for example re-boring of the bore andreplacement of the bush or replacement of the component.

The layer of sealant has both adhesive and sealing properties. The layerof sealant may comprise a conventional sealant or aerospace sealant, forexample an epoxy sealant or two part epoxy sealant such as aerospacesealant PR-2001 under ABP 4-5142. The aerospace sealant may be used inconjunction with an adhesion promoter. Alternatively (or in addition)the layer of sealant may comprise a conventional adhesive or aerospaceadhesive, for example an epoxy adhesive e.g. under AIMS 10-04-002 or atwo-part epoxy adhesive.

The seal member may comprise a solid component which is not an adhesiveor sealant type material.

The seal member may be adapted to substantially cover the layer ofsealant, for example the seal member may cover more than 70% of thelayer of sealant when viewed in plan view along the axis of the bore.Preferably the seal member covers more than 80% or more than 90% or morethan 95% or more than 99% of the area of the layer of sealant.

The seal member may, therefore, protect the layer of sealant fromdegradation, for example due to moisture, chemicals and mechanical wear.The seal member may also help to prevent the ingress of contaminantsthrough the layer of sealant, particularly if the seal member is lesspermeable to contaminants than the layer of sealant or if the propertiesof the layer of sealant become degraded over time.

The seal member may be tougher and less permeable than the layer ofsealant so that the combined effect of the seal member and the layer ofsealant provides a more effective barrier against contamination than alayer of sealant alone.

The seal member may be substantially annular.

The annular seal member may be substantially concentric with the bore.

The annular seal member may be continuous. Alternatively the annularseal member may comprise a split. The split may extend between an innerradial edge and an outer radial edge of the seal member. The split mayallow the seal member to be deformed to generate an opening along asplit line. Therefore if a pin is located within a bush fitted in a boreof a component, the seal member may be fitted to the bush assemblywithout removing the pin, for example by opening the split, passing thepin through the slit, and then closing the split so that the seal memberradially surrounds the pin. The split may therefore increase ease ofinstallation and removal of the seal assembly. The split may comprisemeans for improving sealing performance, for example a scarf joint or alap joint.

The seal member may comprise a lower surface which faces towards thebush and the component. The lower surface of the seal member may engagethe layer of sealant.

The seal member may comprise an inner portion which overlaps with theflange of the bush, and an outer portion which overlaps with the surfaceof the component.

The sealant layer may extend between the inner portion of the sealmember and the flange, and between the outer portion of the seal memberand the surface of the component.

The component may comprise a recess in the surface surrounding the bore,which accommodates the flange of the bush. There may be a gap between anouter edge of the flange and an outer edge of the recess. The recess mayhave a larger diameter than the flange. The seal member may include astep corresponding to an edge of the recess. Alternatively the flangemay sit on a nominal outer surface of the component.

The seal member may include at least one groove formed in the lowersurface of the seal member. The groove(s) may be substantially annular.The groove(s) may be filled with the sealant. A groove or plurality ofgrooves may be provided on the inner portion and/or the outer portion ofthe seal member. If the flange sits within a recess in the surface ofthe component surrounding the bore, a groove or a plurality of groovesformed in the outer portion of the seal member may be provided above therecess and/or beyond the outer edge of the recess.

The layer of sealant may comprise at least one O-ring like portion whichengages and at least substantially fills a groove formed in the lowersurface of the seal member. The O-ring like portions may improve thesealing of the bush assembly and may provide additional protectionagainst the ingress of contaminants, for example if the layer of sealanthas a tendency to lift away from the component. The O-ring like portionsmay also improve the ability of the layer of sealant to securely locateand retain the seal member and may act as an arrestor in the event of acrack or partial failure of the layer of sealant.

The seal member may include a non-porous material.

The seal member may include a plastics material, for example apolyurethane material, or similar. Alternatively the seal member mayinclude an elastomeric material, for example a fluorinated siliconematerial or another rubber material.

The seal member may be sufficiently flexible to accommodate deformationof the bush and/or displacement of the bush relative to the componentunder load, for example load applied to the bush by a pintle pin.Deformation may include the bush assuming an elliptical shape.Displacement may include movement of the bush in an axial directionwithin the bore and/or rotation of the bush within the bore. The sealassembly may, for example, be able to tolerate the bush moving axiallyby up to 1 mm out of the bore.

In some embodiments, the seal member may comprise reinforcement. Thereinforcement may be provided at or near an upper surface of the sealmember facing away from the bush and the component. The reinforcementmay be embedded within a main body of the seal member below the uppersurface of the seal member. The reinforcement may comprise one or morefabric layers, for example a polyester fabric layer. The reinforcementmay increase the durability of the seal and protect the seal member fromdamage during installation of the seal assembly and/or use of the bushassembly.

In some embodiments, the seal member may comprise a main body formed ofa first material and one or more contact elements formed of a secondmaterial which is different to the first material. The contactelement(s) may be provided on the lower surface of the seal member atthe interface between the seal member and the layer of sealant. Thecontact elements may comprise a material which provides a more securebonding surface for the layer of sealant to adhere to than the firstmaterial, thereby increasing the strength and durability of the bondbetween the seal member and the layer of sealant and increasing the lifeof the seal assembly. The contact elements may, for example, comprise aGFRP or CFRP layer. The contact elements may be co-cured or bonded tothe main body of the seal member.

The flange may have a taper of reducing thickness in the radiallyoutward direction. The seal member may have a complimentary taper.

The layer of sealant may extend beyond an outer edge of the seal member.

The layer of sealant may comprise a single continuous layer whichextends substantially under the entire seal member. Alternatively theremay be a discontinuity in the layer of sealant. For example, the layerof sealant may comprise a first portion of sealant material between theinner portion of the seal member and the flange of the bush and a secondportion of sealant material between the outer portion of the seal memberand the component. The first and second portions of sealant material mayeach be substantially annular. There may be a gap between the first andsecond portions of sealant material. The gap may comprise a void. Thevoid may extend substantially around a radial outer edge of the flange.Alternatively the gap may be filled with another portion of sealant,adhesive or filler. The use of multiple discrete portions of sealantwith a gap between the portions may increase the ability of the sealassembly to accommodate deformation and/or displacement of the bush asdiscussed above. The use of multiple discrete portions of sealant mayalso help to arrest propagation of a crack in the event of a partialfailure of the layer of sealant.

The seal assembly may comprise multiple contact elements associated withdifferent portions of sealant material. For example the seal assemblymay comprise a first contact element via which the first portion ofsealant material engages the seal member and a second contact elementvia which the second portion of sealant material engages the sealmember.

The seal member may comprise an integral dust seal portion extendingfrom an upper surface of the seal member facing away from the bush andcomponent. The dust seal may be adapted to form a seal against a secondcomponent which is attached to the component in which the bush is fittedby a pin passing through the bore. The dust seal portion may comprise areinforcement element or biasing element which acts to bias the dustseal portion towards the second component. The biasing element may forexample comprise a metallic or composite rod or strip.

The component may be an aircraft landing gear component. For example,the component may be a main landing gear component such as a mainlanding gear forging or a landing gear rib. Alternatively, the componentmay be any component in an aircraft, or other vehicle, or in any otherapplication.

The method may further comprise the step of: fitting the bush in thebore before arranging the seal member on the bush. The method may beused to seal a bush which is already fitted in a bore, or may be used toseal a bush which is being newly fitted, or re-fitted, in a bore.

The method may further comprise the step of: removing an existing bushfrom the bore before fitting the bush into the bore. The method may,therefore, be used to seal a replacement bush which is replacing a usedbush, for example a bush which has become worn or degraded.

The method may further comprise re-boring the bore before fitting thebush. The original bore may be re-bored to provide a new bore atsubstantially the same location as the original bore, the new borehaving a greater diameter than the original bore. The bush may then befitted in the new bore.

The seal assembly may be retro-fitted to an existing bush fitted in abore of an existing component without modification of the bush or thecomponent.

The method may further comprise placing a tool on the seal member andapplying pressure to the seal member to compress the seal member and thelayer of sealant. By compressing the layer of sealant, the tool mayencourage the layer of sealant to conform to the component and theflange and the seal member, thereby improving the contact between thecomponents of the bush assembly and reducing porosity between thecontacting surfaces, and ensuring correct location of the seal memberover the component and the bush. By compressing the layer of sealant,the seal member may also be encouraged to adhere to the layer ofsealant.

The method may further comprise using the tool to maintain pressure onthe seal member, thereby compressing the seal member and the layer ofsealant, until the layer of sealant is at least partially cured. Theseal member may adhere to the layer of sealant when the layer of sealanthas cured.

The first part and/or the second part of the tool may comprise a portionor portions which are adapted to engage a surface of a bore in which thebush is fitted and/or an inner surface of the bush, thereby centring thetool within the bore.

The centring feature(s) may be circular cylindrical portions of thefirst and/or second parts of the tool. Alternatively, the centringfeatures may take any other shape capable of centring the tool withrespect to the bush and/or the bore by engaging the bore surface and/orthe inner surface of the bush.

The clamping mechanism may pass through the bush. The clamping mechanismmay engage the first part of the tool on one side of the component andengage the second part on an opposing side of the component.

The tool may comprise a seal adapted to prevent sealant from leakingoutside a boundary defined by the tool.

The recess may be adapted to cooperate with a surface of a seal memberforming part of the seal. The seal may be a seal as described inrelation to the first aspect of the invention.

The tool may define an extent to which a layer of sealant extends beyondan outside edge of the seal member.

The tool of the fourth aspect may be used in the method of the thirdaspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 illustrates a main landing gear component for an aircraft;

FIG. 2 illustrates a cross section through a main landing gear componentwith a bush fitted in a bore;

FIG. 3 illustrates a cross section through a bush assembly in accordancewith a first embodiment of the invention;

FIG. 4 illustrates a cross section through the seal member used in thebush assembly of FIG. 3;

FIG. 5 illustrates a cross section through a tool being used to assemblethe bush assembly of FIG. 3;

FIG. 6 illustrates an enlarged view of the cross section through thetool of FIG. 5;

FIG. 7 illustrates a cross section through a bush assembly in accordancewith a second embodiment of the invention;

FIG. 8 illustrates a cross section through the seal member used in thebush assembly of FIG. 7; and

FIG. 9 illustrates a cross section through a bush assembly in accordancewith a third embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENT(S)

An aircraft (not shown) comprises a landing gear assembly. The landinggear assembly comprises a main landing gear component 1, a portion ofwhich is shown in FIG. 1. The component 1 has an outer surface 2 and abore 3 extending through the outer surface and continuing through thethickness of the component for receiving a shaft (not shown). The bore 3has a bore surface 3 a, as shown in FIG. 2, and is surrounded by arecess 4 in the outer surface 2. The bore 3 is provided with a bush 5which is press fitted in the bore 3 and provides an inner surface 7 forrotating engagement with the shaft.

The bush 5 has a tubular body portion 6 and an annular flange portion 9.The body portion 6 is fitted in the bore 3 and provides an inner surface7 for receiving the shaft and an outer surface 8 which engages the boresurface 3 a to hold the bush 5 relative to the component 1. The flangeportion 9 has a planar lower surface 10 which sits against component 1within the recess 4. The flange portion 9 has an outside edge 12 whichextends around and faces away from the body portion 6. The flangeportion 9 tapers towards its outside edge 12 due to a ramp in its uppersurface 11.

A seal member 20, arranged as an annular ring, sits over the flangeportion 9 of the bush 5 and the outer surface of the component 1covering the outside edge 12 of the flange portion 9, as shown in FIG.3. The seal member 20 has an inner portion 20 a which sits above theflange portion 9 of the bush 5 and an outer portion 20 b which sitsabove the outer surface of the component 1, as shown in FIG. 4. The sealmember 20 has an upper surface which faces away from the component 1 anda lower surface which faces towards the component 1 and the bush 5. Thelower surface of the seal member 20 is shaped to correspond to thecontours of the flange 9 and the component 1, and has a ramp providing ataper in the thickness of the seal member towards the centre of the borewhich corresponds to the taper in the thickness of the flange portion 9towards its outside edge 12. The lower surface of the seal member 20also has a step which corresponds to the step provided by the recess 4.The lower surface is provided with grooves 21 in its inner and outerportions 20 a, 20 b which extend annularly around the seal member 20.The seal member 20 is made from polyurethane and is flexible, resilientand non-porous.

A sealant layer 22 of aerospace grade sealant, for example aerospaceepoxy adhesive under ABP 4-5142 (or another sealant or adhesive materialas described above), is disposed between the seal member 20 and theflange portion 9 and between the seal member 20 and the component 1, asshown in FIG. 3. The sealant layer substantially fills the volume belowthe seal member 20, and has a thickness of approximately 0.2 mm betweenthe flange portion 9 and the seal member and between the outer surface 2of the component 1 and the seal member for optimised adhesion andsealing performance. The sealant layer 22 substantially fills thegrooves 21, thereby forming O-ring like protrusions 23 in the sealantlayer 22. The sealant layer extends slightly beyond the outer edge ofthe seal member, forming an outer-most portion 22 a of the sealant layerwhich substantially covers the outer edge of the seal member 20. Theseal member 20 substantially covers the sealant layer 22 so that only asmall portion of the sealant layer is exposed to the atmosphere.

The seal member 20 and the sealant layer 22 form a seal assembly whichseals the interface between the flange portion 9 and the component 1.The sealant layer 22 also seals the gap between the seal member 20 andthe external surface of the component 1. The seal assembly reduces theingress of contaminants including water, oil, dirt and debris betweenthe flange portion 9 and the outer surface of the component 1. The sealassembly, therefore, reduces contamination of the interface between theouter surface 8 of the body portion 6 and the bore surface 3 a due toingress of contaminants under the flange portion 9. In this way,degradation of the bush 5 and the bore surface 3 over time are reduced,and so the life of the bush assembly is increased. The bush 5 is,therefore, less likely to require frequent replacement, and the boresurface 3 a of the component 1 is less likely to be degraded to a pointat which re-boring of the bore 3 or even replacement of the entire mainlanding gear component 1 becomes necessary.

The seal member 20 is non-porous and tougher than the sealant layer 22,and substantially covers the sealant layer, thereby protecting it fromexposure to moisture, chemicals and mechanical wear. In this way, theseal member 20 reduces the susceptibility of the sealant layer 22 todamage and degradation during use of the bush assembly, so that theeffective life of the sealant layer 22 is increased and the sealassembly is less likely to experience a significant reduction in sealingperformance over time. The interface between the outer surface 8 of thebody portion 6 and the bore surface 3 a is, therefore, less likely tobecome contaminated, and the need for non-destructive tests to assessthe performance of the sealant layer is reduced.

The seal member 20 is less permeable than the sealant layer 22 which itcovers, so that the seal assembly provides a more effective barrieragainst contamination than a layer of sealant alone. The seal member 20,therefore, increases the sealing performance of the seal assembly sothat the interface between the outer surface 8 of the body portion 6 andthe bore surface 3 a is less likely to become contaminated. Theadvantage becomes increasingly significant as the sealant layer 22 agesbecause the sealant layer tends to become more porous and brittle overtime, for example due to age hardening, but the sealant layer remainssubstantially covered by the non-porous seal member 20 whichsubstantially prevents the exposure of the sealant layer tocontaminants.

The O-ring like protrusions 23 formed in the sealant layer 22 improvethe sealing of the bush assembly against contaminants and provideadditional protection against contaminant ingress if part of the sealantlayer 22 should tend to lift away from the component 1. The O-ring likeprotrusions 23 also assist with secure location of the seal member 20 onthe sealant layer 22.

The outer-most portion of the sealant layer 22 a, which covers the outeredge of the seal member 20, seals the edge of the seal member to preventthe ingress of contaminants under the seal member. The outer-mostportion 22 a acts to increase the path length for contaminants enteringthe seal assembly and provides an additional corner between the sealmember 20 and the sealant layer, which any contaminants would need tonavigate before reaching the interface between the bush 5 and the boresurface 3 a.

The recess 4 around the bore 3 and the taper provided in the uppersurface 11 of the flange portion 9 of the bush 5 allow the extent of thebush assembly protruding outwards from the outer surface 2 of thecomponent 1 to be minimised (i.e. the seal assembly is only just proudof the outer surface) so that the bush assembly is compact and lesssusceptible to damage.

The bush and seal member are assembled by pressing the bush 5 into thebore 3 in the component 1; applying a layer of aerospace grade sealantover the flange portion 9 of the bush 5 and the component 1 to form thesealant layer 22; placing the seal member 20 over the bush and component1; and applying pressure to the bush assembly using a clamping tool 24,as shown in FIG. 5.

The tool comprises an upper part 24 a, a lower part 24 b and a stud 24c. The upper part 24 a has a working surface which is adapted to engagethe seal member 20, while the lower part 24 b engages the surface of thecomponent 1 which faces away from the seal assembly. The stud 24 c has athreaded end which is received into a threaded recess in the upper part24 a. The stud 24 c passes through the bore and engages the upper part24 a on one side of the component (the side on which the seal assemblyis provided) and the second part 24 b on the opposing side of thecomponent. The stud 24 c is rotated to bring the upper and lower parts24 a and 24 b together, thereby applying a clamping force to the sealassembly. The upper and lower parts 24 a, 24 b each have cylindricalsurfaces 25 a and 25 b which engage the inner surface 7 of the bodyportion 6 of the bush 5 and act as centring means to ensure that theaxis of the tool is concentric with the bore 3.

The working surface extends beyond the outer edge of the seal member 20to define the extent to which the sealant layer 22 extends beyond theoutside edge of the seal member, as shown in FIG. 6. The tool 24 alsocomprises a rubber O-ring type seal 26, as shown in FIG. 6, whichprevents the sealant layer 22 from leaking outside the tool even whenthe sealant layer is compressed.

The tool 24 applies a light clamping force to the seal member 20 whichcompresses the sealant layer 22. By compressing the sealant layer 22beneath the seal member 20, the sealant layer is encouraged to conformto the surfaces of the component 1, the flange portion 9 of the bush 5and the seal member 20, thereby improving the contact between thecomponents of the seal assembly and reducing porosity between thecontacting surfaces. The tool 24 also helps to ensure correct locationof the seal member 20 over the component 1 and the bush 5, and to ensurethat the seal member 20 adheres to the sealant layer 22. The tool 24 isused to maintain pressure on the seal assembly for at least 4 hoursuntil the sealant layer 22 is at least partially cured. The rate atwhich the sealant cures is dependent on the sealant material used andthe conditions in which the sealant layer 22 is allowed to cure. Theappropriate time period for which the seal assembly is clamped by thetool 24 therefore depends on the choice of sealant and the curingconditions.

In an alternative embodiment, the seal member 20 and sealant layer 22are applied to a used bush 5 which is already installed in a mainlanding gear component 1 of an in service aircraft. The seal assemblymay, therefore, be applied to an aircraft having a used bush.Alternatively, when the seal assembly is installed on an in serviceaircraft, a used bush may be removed from the bore 3 before thereplacement bush 5 is fitted in the bore. If the bore surface 3 a of themain landing gear component 1 has become degraded, for example due tocontamination of the interface between the bore surface 3 a and theouter surface 8 of the body portion 6 of the bush 5, a boring tool isused to re-bore the bore 3 to provide a new bore surface into which thebush is fitted. The new bore is at the same location as the originalbore and has a greater diameter. The replacement bush 5 therefore has agreater diameter than the used bush which is replaced.

FIG. 7 illustrates a cross section through a bush assembly in accordancewith a second embodiment of the invention. The bush assembly of FIG. 7is a modified version of that shown in FIGS. 3 and 4 and the samereference numbers followed by a prime (′) have been used for identicalor equivalent components. The sealant layer comprises a first portion35′ of aerospace epoxy adhesive (or another sealant or adhesive materialas described above) between the inner portion of the seal member and theflange of the bush 5′ and a second portion 36′ of aerospace epoxyadhesive (or another sealant or adhesive material as described above)between the outer portion of the seal member and the component 1′. Thereis a gap 31′ between the first and second portions of sealant material.The seal member comprises two grooves 21′ in its lower surface. Bothgrooves are formed in the outer portion of the seal member such that twoO-ring like protrusions 23′ are formed in the second portion of epoxyadhesive 36′ between the seal member and the component 1′. The bushassembly further comprises a dust shield 32′ attached to the flange ofthe bush 5′ which seals against a second component 100′ connected by apin 101′ to prevent the ingress of dust and other debris between thefirst and second components.

FIG. 8 illustrates a cross section through the seal member 20′ of FIG.7. The seal member is formed of a fluorinated silicone and comprises areinforcement layer 33′ of polyester fabric. The seal member 20′ furthercomprises an annular inner contact element 34′ at the interface betweenthe inner portion of the seal member and the first portion 35′ of thesealant layer and an annular outer contact element 34′ at the interfacebetween the outer portion of the seal member and the second portion 36′of the sealant layer. The contact elements 34′ comprise a glass fibrefabric pre-preg which is co-cured with the main body of the seal member20′. The contact elements 34′ increase the strength of the bond betweenthe seal member 20′ and the sealant layer.

FIG. 9 illustrates a cross section through a bush assembly in accordancewith a third embodiment of the invention. The same reference numbersfollowed by a double prime (″) have been used for identical orequivalent components. In the bush assembly of FIG. 9 a seal member 20″includes an integral dust seal portion 200″ extending outwardly from theupper surface of the seal member and forming a seal against the secondcomponent 100″. The dust seal portion 200″ includes an integral biasingelement 201″ which acts to bias the dust seal portion towards the secondcomponent.

In an alternative embodiment, the seal member may comprise any knownnon-porous material.

In an alternative embodiment, the bush may have a split down one side ormay be provided in multiple segments.

In an alternative embodiment, the seal member may comprise any number ofgrooves which form O-ring like protrusions in the sealant layer, or nogrooves.

In an alternative embodiment, the outside edge 12 of the flange portion9 may extend up to the outside diameter of the recess 4.

In an alternative embodiment, the component 1 may not comprise a recesssurrounding the bore 3, so that the lower surface 10 of the flangeportion 9 sits on the outer surface of the component.

In an alternative embodiment, the sealant layer may be applied to thelower surface of the seal member before the seal member is arranged onthe main landing gear component.

In an alternative embodiment, the bush assembly may be used in anyaircraft or non aircraft application in which a bore in a component isprovided with a bush.

Although the invention has been described above with reference to one ormore preferred embodiments, it will be appreciated that various changesor modifications may be made without departing from the scope of theinvention as defined in the appended claims. In particular, one or allof the features of any one of the embodiments may be combined with anyof the features of any other embodiment or with a bush assembly ormethod according to the appended claims.

1-14. (canceled)
 15. A clamping tool for applying a clamping force forsealing a bush installed in a bore in a component, the tool comprising afirst part, a second part and a clamping mechanism; wherein the firstpart comprises a recess which is adapted to engage a seal; the secondpart is adapted to engage a surface of the component which opposes andfaces away from a surface of the component on which the seal isprovided; the clamping mechanism is operable to move the first partrelative to the second part, thereby applying a clamping force to theseal; and wherein the clamping tool includes centring means for centringthe clamping tool relative to the bush.
 16. A clamping tool according toclaim 15, wherein the tool has a longitudinal axis.
 17. A clamping toolaccording to claim 16, wherein the clamping mechanism is operable tomove the first part relative to the second part along the longitudinalaxis of the tool.
 18. A clamping tool according to claim 16, wherein thecentring means is
 19. A clamping tool according to claim 15, wherein thefirst part has a working surface which is adapted to engage the surfaceof the component.
 20. A clamping tool according to claim 15, wherein theclamping mechanism includes a stud having a threaded end which isthreadedly engaged with the first part and with the second part.
 21. Aclamping tool according to claim 15, wherein the first part has aworking surface adapted to engage the seal.
 22. A clamping toolaccording to claim 21, wherein the centring means comprises acylindrical surface projecting from the working surface of the firstpart.
 23. A clamping tool according to claim 21, wherein the recess isformed in the working surface of the first part.
 24. A clamping toolaccording to claim 21, further comprising an O-ring seal in a grooveformed in the working surface of the first part.
 25. A clamping toolaccording to claim 23, further comprising an O-ring seal in a grooveformed in the working surface of the first part, wherein the groove hasa larger diameter than a diameter of the recess.
 26. A clamping toolaccording to claim 15, wherein the second part has a working surfaceadapted to engage the surface of the component which opposes and facesaway from a surface of the component on which the seal is provided. 27.A clamping tool according to claim 24, wherein the centring meanscomprises a cylindrical surface projecting from the working surface ofthe second part.